The present invention relates to a manufacturing method for thin film magnetic heads utilized in magnetic disk devices, and relates in particular to a manufacturing method for thin film magnetic heads utilized for reading.
The thin film magnetic heads mounted in HDD require a narrow track width and narrow gap length and high sensitivity in order to keep pace with the ever higher recording density of HDD. The thin film magnetic head currently utilizes a combination of a write (recording) head and a read head. The read heads are mainly GMR heads that utilize the GMR effect. These GMR heads are CIP (Current In Plane) type heads that allow electrical signals to flow in the film parallel to the sensor film surface. There has been intensive work into developing CPP-GMR (Current Perpendicular to a Plane Giant Magneto-Resistive Effect) and TMR (Tunneling Magneto-Resistive effect) heads that possess an excellent high output even with narrow track width and narrow gap length, in order to keep pace with still further future advances towards higher recording density. Unlike the conventional GMR head, that uses a CIP type head where electrical signals flow parallel within the film surface, the significant difference in the TMR head and CPP-GMR head is that a CPP head is used where electrical signals flow in a direction perpendicular to the film surface.
Prior technology relating to the CPP head that serves as the CPP-GMR head is disclosed in JP-A No. 198000/2003. The bottom electrode (lower pole) includes a protrusion that contacts the sensor film, and by making the width contacting the sensor film of the upper lead (top pole) smaller than the lower lead (bottom pole), the alignment margin can be improved and a tiny contact section formed. The technology in JP-A No. 298144/2003 contains a lower pole with a protruding shape resembling that of JP-A No. 198000/2003. In this laid-open technology, the protruding section is planarized, and a more uniform sensor film can be formed, so that characteristics are improved.
A lift-off process is normally used as shown in FIG. 1 for forming the track widths. As shown in FIG. 1(a), a lift-off pattern 3 is formed on the sensor film 2 over the bottom shield 1. This cross sectional shape of this lift-off pattern 3 possesses an undercut. Etching of the sensor film 2 is performed as shown in FIG. 1(b) by utilizing this lift-off pattern 3 as a mask. Next, after forming the insulating film 4 (and others) as shown in FIG. 1(c), unnecessary sections on the insulating film are removed by lift-off using a solvent process such as with a remover as shown in FIG. 1(d). This undercut makes the etching and lift-off easy to perform after forming the film.
Other processes for forming the track width have been proposed. A method disclosed in JP-A No. 123916/2002 proposes a thin-film magnetic head embedded in the surrounding sensor film by planarizing film and planarizing technology. A method disclosed in JP-A No. 132509/2003 proposes a thin-film magnetic head where the track width is formed by CMP (chemical mechanical polishing) and milling. A structure in which a shield film is installed on the side of the sensor film to prevent side-reading has also been proposed. One example is disclosed in JP-A No. 264324/2003.